Then, eight hours later, six people and a police officer were run down by a car in a separate attack as police chased the van's driver. MSNBC reported that police shot dead five of the attackers. The suspects were wearing fake suicide belts.

ISIS has claimed responsibility for the deadly incident, which Spain is treating as a terror attack.

Witnesses said they watched victims "flying into the air."

Ali Shirazinia was riding his bike down the street of the popular tourist destination when he heard screaming.

"I looked over to my left and I saw all of the people along the promenade kind of split into two -- some going right, the rest coming really towards me, screaming and running as fast as they could," he told CNN. "I saw people flying into the air and everybody was kind of running into the shops on either side of the Ramblas, and a lot of people were in shock."